WASHINGTON » Behind the desk at his Capitol office, Sen. Richard J. Durbin of Illinois keeps a framed copy of his mother’s naturalization certificate.

She was a toddler when she arrived from Lithuania and was 26 when she became a citizen. She had grown old by the time her son asked what had happened to her citizenship papers.

"She wasn’t in the best of shape then, but she pops up off the couch, and she’s gone three minutes — tops — and comes in with this old, beat-up brown envelope, hands it to me," Durbin recalled in an interview this year. A slip of paper fluttered out, the filing fee receipt she had kept all those years.

"That was my mom. When we talk about immigration, I kind of have a personal side to the story."

As the immigration debate unfolds, senators have begun telling their own stories of immigration and the immigrants they have known, a treasure trove of American history spilling forward on the Senate floor.

The narratives, some recited with fervor, others more tentatively, show how the deeply personal experiences of senators and their families inform the political debate on both sides.

Newly elected Sen. Mazie Hirono, D-Hawaii, the only immigrant serving in the Senate, arrived as a young girl when her mother fled what the senator has described in her campaign and on other occasions as an abusive husband in Japan.

The 7-year-old did not know English when she made the ocean voyage on the passenger ship President Cleveland.

Landing in Hono­lulu, she worked as a student cashier in elementary school to pay for her lunches. A few years later, in 1959, when Hawaii became a state, she became a naturalized citizen.

"The amazing thing about this country is millions of families have stories like mine," Hirono said in the Senate, where she is working to extend certain immigration rights to women and families. "If I had not been able to come to this country, who knows where I’d be today. But I can tell you that I would not have had anything close to the opportunities this great country has given to me."

Two Republican sons of immigrants, Sen. Marco Rubio of Florida and Sen. Ted Cruz of Texas, both 42, share similar family histories as children of Cuban exiles. But they take radically different approaches to changing the nation’s immigration laws.

Rubio, a leader of the immigration overhaul effort, speaks of his parents landing in the U.S. before he was born, after leaving Cuba a couple of years before Fidel Castro’s revolution. His mother clerked at a Kmart while his dad tended bar in ballrooms like those where Rubio now gives speeches.

Cruz, who was born an American citizen, has become one of the most prominent opponents of the bill Rubio champions, which would provide current unauthorized immigrants a path to citizenship. He tells his father’s story of having fled Cuba, washed dishes to pay for college, married an American and started a business.

Those who are familiar with immigrants and the experiences of newcomers are likely to empathize with the problems inherent in the complex system of immigration laws, even if they do not always agree on what policy conclusions to draw, experts say.

"If they don’t know undocumented immigrants, they’re afraid of them," said Gabriel Sanchez, an associate professor at the University of New Mexico and director of research at Latino Decisions, a polling firm. "It really just comes down to basic psychology: You remove the fear factor and it allows people to think about it from a different perspective."

Before he was elected to public office, Sen. Jeff Flake, R-Ariz., was executive director at the Goldwater Institute. He was a fiscally conservative hawk in a state that takes a hard line against illegal immigration.

But in his youth, Flake, a fifth-generation Arizonan, grew up alongside migrant farmworkers from Mexico — many of them without legal immigration status — on his family’s cattle ranch and farm in the northern part of the state.

"I could never look at the population we have here in Arizona — it’s a big population of those who are here illegally — and put them all in one criminal class," said Flake, who is a member of the bipartisan group that crafted the immigration overhaul proposal. "It’s never rung true for me."

Some senators acknowledge that their immigrant tales may not be the most original, but the stories help guide their thinking.

Sen. Amy Klobuchar, D-Minn., has shrugged that part of her story is a cliché — Swiss grandparents on her mother’s side who came to the U.S. and opened a cheese shop in Wisconsin. Her father’s father, from Slovenia, mined iron ore. But their granddaughter became first woman Minnesota elected to the Senate.

"I stand here today on the shoulders of immigrants," she said in the Senate last week. "It could not have been possible in a country that didn’t open its arms to the risk-takers, pilgrims and pioneers of the world."